1. Field of the Invention
The present invention relates to a micro-electro-mechanical device which has a microstructure and a semiconductor element, and a manufacturing method therefor.
2. Description of the Related Art
In recent years, a micro mechanical system called MEMS is actively researched. MEMS is an abbreviated name of a micro-electro-mechanical system, which is sometimes simply called a micromachine. A micromachine in general corresponds to a minute device in which “a movable microstructure having a three-dimensional structure” is integrated using a semiconductor minute processing technique. The microstructure has a three-dimensional structure, a movable portion, and a space for moving.
A micromachine can control its microstructure by using an electronic circuit. Therefore, it is said that an autonomous decentralized type system can be formed which performs a series of operations by processing information obtained by a sensor in an electronic circuit and executing the operation through an actuator or the like, instead of a central processing control type system such as a conventional device using a computer.
Many strudies have been made on a micromachine. For example, an advanced MEMS wafer level package is proposed to overcome a problem that a manufacturing process cannot be used with equipment for wafer manufacturing and plastic assembly (Patent Document 1).
In addition, a method of manufacturing a semiconductor package is proposed in which a microstructure and a semiconductor element are separately formed over countering substrates and are electrically connected to each other (Patent Document 2).
In addition, there is a document of a thin-film-shaped and crystallized mechanical device and an electro-mechanical device called MEMS (Patent Document 3). In the Patent Document 3, an amorphous material, a nanocrystalline material, a microcrystalline material, and a polycrystalline material are listed as a starting material of a thin film. As the material thereof, silicon, germanium, silicon germanium, an anisotropic dielectric material, an anisotropic piezoelectric material, copper, aluminum, tantalum, and titanium are listed. In addition, it is described that a thin-film-shaped amorphous silicon layer is formed over a glass substrate, then, crystallized. In the crystallization, laser irradiation is controlled so that in an inner part, a crystalline property which can provide favorable mechanical characteristics is realized.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-144117    [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-297876    [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-1201
As described in Patent Document 1, a microstructure in a micromachine is formed by a process using a silicon wafer. In particular, in order to obtain a material with sufficient thickness and strength to manufacture a microstructure, most micromachines in practical use are manufactured using silicon wafers.
In addition, in accordance with a mass productivity of a micromachine having a minute structure, reduction in manufacturing cost is desired. Therefore, a method in which a microstructure and a semiconductor element controlling the microstructure are integrated is desired. However, when integrating a microstructure and a semiconductor element, the manufacturing process becomes complicated since the manufacturing process of the microstructure and that of the semiconductor element are different, e.g., etching of a sacrificial layer. Since the processes are different, when integrating the microstructure and the semiconductor element, there is a possibility that the microstructure or the semiconductor element is damaged and does not operate. Therefore, most micromachines in practical use have microstructures and semiconductor elements manufactured in different processes.